Al-Kāfi - Volume 3 > Obligation of Friday Salah (prayer)
Hadith #3

3ـ عَلِيٌّ عَنْ أَبِيهِ عَنْ حَمَّادٍ عَنْ حَرِيزٍ عَنِ ابْنِ مُسْلِمٍ قَالَ سَأَلْتُ أَبَا عَبْدِ الله (عَلَيْهِ الْسَّلام) عَنِ الْجُمُعَةِ فَقَالَ تَجِبُ عَلَى مَنْ كَانَ مِنْهَا عَلَى رَأْسِ فَرْسَخَيْنِ فَإِذَا زَادَ عَلَى ذَلِكَ فَلَيْسَ عَلَيْهِ شَيْ‏ءٌ.

3. Ali has narrated from his father from Hammad from Hariz from ibn Muslim who has said the following: “I once asked abu ‘Abd Allah, ‘Alayhi al-Salam, about Friday. He (the Imam) said, ‘It (Friday Salah (prayer)) is obligatory up on those who live within two farsakh. If the distance is more than this then it is not obligatory on him.’”